Inkjet recording method using colored ink

Abstract

Purpose is to provide an inkjet recording method for forming high-quality color image on a thick recording medium having low thermal conductance rate. The present invention is a single-pass inkjet recording method using an ink set including at least two active ray-curing color inks, and a recording medium having thermal conductivity of less than 0.10 W/(m·K) and thickness of 0.4 mm or more. The ink set containing two color inks satisfy only condition (a), and the ink set containing three or more color inks satisfy conditions (a) and (b): (a) most downstream color ink has a gelation temperature which is 3.0° C. to 15.0° C. higher than that of most upstream color ink, and (b) second or subsequent color ink from the most upstream position in conveyance direction has a gelation temperature which is the same as or higher than that of an adjacent color ink at the upstream position.

The invention claimed is: 
     
       1. An inkjet recording method of single pass recording type, the recording method comprising:
 using an ink set comprising at least two actinic radiation-curable color inks each comprising a photocurable compound, a gelling agent, and a colorant to jet out droplets of a plurality of color inks, thereby landing the inks onto a recording medium; and 
 irradiating the color inks landed onto the recording medium with actinic radiation to cure the inks, 
 wherein: 
 when the ink set contains two different color inks, the ink set satisfies only condition (a), and when the ink set contains three or more different color inks, the ink set satisfies both conditions (a) and (b), the conditions (a) and (b) being: 
 (a) a color ink at a most downstream position has a gelation temperature which is 3.0° C. to 15.0° C. higher than a gelation temperature of a color ink at a most upstream position, and 
 (b) a second or subsequent color ink as counted from the most upstream position in a conveyance direction has a gelation temperature which is the same as or higher than a gelation temperature of an adjacent color ink at an upstream side; and 
 the recording medium has a thermal conductivity of less than 0.10 W/(m·K) and has a thickness of 0.4 mm or more. 
 
     
     
       2. The recording method according to  claim 1 , wherein the recording medium is a paper having a basis weight of 200 g/m 2  or more, or is a thin corrugated cardboard comprising a corrugated medium and a liner. 
     
     
       3. The recording method according to  claim 1 , wherein in condition (a), the gelation temperature of the second or subsequent color ink is higher than the gelation temperature of the adjacent color ink at the upstream position. 
     
     
       4. The recording method according to  claim 1 , wherein the ink set comprises 4 color inks of yellow (Y), magenta (M), cyan (C), and black (K), and further comprises a different color ink. 
     
     
       5. The recording method according to  claim 1 , wherein the color ink at the most downstream position is a color ink having a highest brightness in the ink set. 
     
     
       6. The recording method according to  claim 1 , wherein each color ink contained in the ink set has a gelation temperature in a range of from 30° C. to 60° C. 
     
     
       7. The recording method according to  claim 1 , wherein the gelling agent comprises at least one compound selected from the group consisting of a compound represented by the following formula (G1) and a compound represented by the following formula (G2):
   R1—CO—R2; and  Formula (G1):
 
   R3—COO—R4,  Formula (G2):
 
 wherein R1 to R4 each independently represents a hydrocarbon group comprising a straight-chain moiety having 12 or more carbon atoms and optionally comprising an additional branched moiety.